This invention relates to polymer films; and in particular, to laminated polymer films possessing water vapor transmission barrier capability.
U.S. Pat. No. 4,377,616, the contents of which are incorporated by reference herein, discloses an opaque biaxially oriented polymer film structure comprising a thermoplastic polymer matrix core layer possessing numerous voids, a substantial number of which contain at least one spherical void-initiating particle, and transparent skin layers adhering to the surfaces of the core layer. The unique structure of the core layer imparts a much higher degree of opacity, possibly due to the effects of light scattering, than that possible by the use of opacifying pigment alone.
There is no suggestion, however, in U.S. Pat. No. 4,377,616 of incorporating the film structure disclosed therein in a laminate possessing a water vapor transmission barrier layer.